Smoke (mist) not working for existing file
No one , Not the blender file , not the model , not the primitives , not the simulator None of them is at fault.When you make a simulation , you also bake it , and im sure you also did that , if you bake the simulation , what it does is that it records the simulations animation so that it doesn't have to do heavy calculation it does while making the simulation for the first time , so try rebaking and come back again